1. Field of the Invention
There is continuing interest in developing new, simpler and more rapid techniques to measure the presence of an analyte in a sample suspected of containing an analyte. The analyte may be any of a wide variety of materials, such as drugs, naturally occurring physiological compounds, pollutants, fine chemicals, contaminants, or the like. In many cases, speed is important for the measurement, particularly with certain physiologically active compounds. In other situations, convenience can be a major consideration.
One convenient technique which has found wide application is the use of a "dip stick." Having a solid rod or film which can be dipped in a sample and then subsequently processed to produce a signal based on the amount of analyte in the original sample can provide many conveniences. There is ample instrumentation to measure a signal, such as light absorption or fluorescence, of a compound bound to a solid surface. Also, the dip stick allows for convenient handling, transfers, separations, and the like.
In developing an assay, it is desirable that there be a minimum number of steps and transfers in performing the assay, as well as a minimum number of separate reagents. Therefore, while a dip stick adds a convenience to separations, the separations in themselves are undesirable. Furthermore, the fewer the reagents that have to be packaged, added, and formulated, the fewer the errors which will be introduced into the assay and the greater economies and convenience of the assay.
It is therefore desirable to develop new assay methods, particularly employing rigid solid surfaces which may or may not be separated from the assay medium for measurement, where the signal may be developed without concern as to the presence of reagents in the solution affecting the observed signal on the solid surface.
2. Brief Description of the Prior Art
Patents concerned with various immobilized reagents in different types of test strips include U.S. Pat. Nos. 3,993,451; 4,038,485; 4,046,514; 4,129,417; 4,133,639; and 4,160,008, and Ger. Offen. 2,636,244. Patents disclosing a variety of methods involving separations of bound and unbound antigen include U.S. Pat. Nos. Re. 29,169; 3,949,064; 3,984,533; 3,985,867; 4,020,151; 4,039,652; 4,067,959*; 4,108,972; 4,145,406; and 4,168,146*. FNT (*Patents of particular interest)